CN115022147A

CN115022147A - Method for realizing cross-protocol coexistence based on WiFi payload coding

Info

Publication number: CN115022147A
Application number: CN202210597785.XA
Authority: CN
Inventors: 姚俊梅; 黄皓朗; 谢瑞桃; 伍楷舜
Original assignee: Shenzhen University
Current assignee: Shenzhen University
Priority date: 2022-05-30
Filing date: 2022-05-30
Publication date: 2022-09-06
Anticipated expiration: 2042-05-30
Also published as: CN115022147B

Abstract

The invention relates to a method for realizing cross-protocol coexistence based on WiFi payload coding, which is used for reducing the WiFi signal power on a first signal channel by setting a lowest constellation point in an overlapped subcarrier of WiFi and a first signal for a first signal interfered by a WiFi signal. The present invention is based on a WiFi subcarrier level energy reduction mechanism to enhance the transmission of the first signal. The method works in an application layer, reduces the WiFi signal power on a first signal channel by setting a constellation point with the lowest power in the overlapping subcarriers of the WiFi and a first signal, reduces the interference of the WiFi on a first signal link, and is beneficial to the successful transmission of the first signal, so that the method is completely compatible with standard physical and MAC layer processes without changing commercial WiFi and first signal transmitting equipment.

Description

Method for realizing cross-protocol coexistence based on WiFi payload coding

Technical Field

The present disclosure relates to the field of heterogeneous wireless networks, and in particular, to a method for implementing cross-protocol coexistence based on WiFi payload encoding.

Background

The proliferation of the internet of things has led to an exponential increase in the number of wireless devices. The wireless device adopts heterogeneous wireless technologies, and each technology has a suitable application scene due to respective advantages and disadvantages. In the crowded ISM (Industrial Scientific Medical) band, heterogeneous wireless devices inevitably operate in overlapping channels, resulting in a serious cross-protocol coexistence problem.

The main current solution to the Cross-protocol Coexistence (Cross-Technology collaboration) problem is interference avoidance, which mainly includes the following design concepts:

(1) cross-protocol interference is combated with physical layer solutions such as: a new ZigBee packet is designed, so that more redundancy is provided, and WiFi interference is relieved. Alternatively, the WiFi and Zigbee signals are separated into different data streams using multiple-input multiple-output (MIMO) technology and interference cancellation technology. Or, the ZigBee device detects that cross-protocol interference exists in the damaged message, and then recovers the message.

(2) Protocol design is carried out by exchanging coordination information among heterogeneous devices, for example, visibility of ZigBee to WiFi is improved by enabling ZigBee devices to transmit specially designed signals, and therefore the WiFi devices keep silent in the ZigBee transmission process. Alternatively, a WiFi device is caused to transmit coordination information to ZigBee devices via a customized preamble, scheduling their transmissions. Alternatively, with emerging cross-technology communication (CTC), interference management is achieved by enabling explicit coordination between heterogeneous devices. For example, data transmission of all WiFi and ZigBee devices is coordinated through the WiFi AP, so as to avoid interference, thereby achieving higher network throughput. Or, a network layer is designed for CTC, and a server schedules ZigBee transmission; or, a customized gateway is designed, so that concurrent transmission of WiFi and ZigBee data streams in the same frequency band is realized, and transmission delay is reduced. Or, efficient radio frequency channel allocation is achieved by utilizing bidirectional coordination among heterogeneous devices.

(3) Cross-protocol interference is avoided by reserving channels. For example, the ZigBee device first identifies an 802.11b WiFi channel, and then sends its own data packet on the guard band of WiFi traffic, avoiding cross-protocol interference.

The problems of the design ideas are as follows: if a physical layer solution is used to combat cross-protocol interference, hardware modifications are often required, even new transceiver designs are required, which cannot be applied to existing devices; if the protocol design is carried out by exchanging the coordination information between heterogeneous devices, additional packet transmission is caused, and substantial modification of the standard is required; if a reserved channel is used, it requires all WiFi devices to operate on non-overlapping channels, which is difficult to meet in the congested ISM band.

Disclosure of Invention

In view of the above prior art, the technical problem to be solved by the present invention is to provide a method that is completely compatible with the standard physical and MAC layers, and can alleviate the interference of WiFi to other protocol signals without changing hardware devices.

In order to solve the technical problems, the technical scheme of the invention is as follows:

in a first aspect, the invention provides a method for realizing cross-protocol coexistence based on WiFi payload coding, for a first signal interfered by a WiFi signal, a constellation point with the lowest power is set in a subcarrier where the WiFi and the first signal are overlapped, and the power of the WiFi signal on a first signal channel is reduced.

In the above technical solution, the present invention is based on a WiFi subcarrier level energy reduction mechanism to enhance the transmission of the first signal. The method works in an application layer, reduces the WiFi signal power on a first signal channel by setting a constellation point with the lowest power in the overlapping subcarrier of the WiFi and a first signal, reduces the interference of the WiFi on a first signal link, and is beneficial to the successful transmission of the first signal, so that the method is completely compatible with standard physical and MAC layer processes, and commercial WiFi and first signal transmitting equipment do not need to be changed.

In the above technical solution, the setting includes the steps of:

modulating WiFi by an orthogonal frequency division multiplexing technology to determine a constellation point with the lowest power;

for each constellation point with the lowest power, determining a bit set which enables the power to be the lowest in each point, and taking the bit set as an effective bit set;

the set of valid bits is made the specified set of bits, but the other bits in the quadrature amplitude modulation point are arbitrary.

In the above technical solution, the specified bit set is obtained by:

sequentially carrying out effective load coding, scrambling, convolution coding and interleaving operation on WiFi bit data;

the payload encoding of the WiFi bit data is to insert additional bits in the WiFi bit data.

In the above technical solution, the extra bit is obtained by the following steps:

using data obtained after scrambling WiFi bit data as a first bit set, using an effective bit set in front of an interleaver as a second bit set, wherein elements in the second bit set are formed by values and positions of effective bits;

setting a third bit set as a data set for carrying out effective load coding on WiFi bit data and then scrambling;

acquiring the 1 st data of the first bit set as a current first bit, and acquiring the 1 st effective bit in the second bit set as a current second bit;

acquiring first data in a third bit set as a current third bit;

marking S: comparing and judging the subscript of the current third bit and the position size in the current second bit:

if no extra bit needs to be inserted, the current third bit is equal to the current first bit; a step of obtaining the next first bit as the current first bit, setting the next data in the third bit set as the current third bit, and returning to the mark S;

if M1 extra bits are needed to be inserted, and M1 is more than 0, M2-M1 third bits used for convolutional code conversion are obtained from a third bit set according to the M2 bit quantity used for convolutional code conversion, wherein M2 is more than 0; acquiring the next second bit from the current second bit in the second bit set until M1-1 second bits are acquired, and substituting the values of the M2-M1 third bits and the M1 second bits into a convolutional coding equation or a convolutional coding equation set to solve extra bits;

inserting the solved M1 extra bits into the third set of bits and making the current third bit equal to the current first bit; acquiring the next first bit as the current first bit, acquiring an M1 th second bit after the current second bit as the current second bit, and acquiring the next data in the third bit set as the current third bit; and returning to the step of marking S.

In the above technical solution, the inserted M1 extra bits and M2-M1 third bits are convolution-encoded to generate M1 second bits, so that solving for the extra bits is equivalent to performing inverse solution on the convolution encoding. Although the convolutional encoder increases the redundancy of data bits, an arbitrary bit sequence cannot be generated, and the process is not in one-to-one correspondence, the redundant bit number can be determined by utilizing the characteristics of the convolutional encoder. Also, the interleaving process spreads the effective bits far enough so that the inverse of convolutional coding is necessarily solvable.

In the above technical solution, when the convolutional coding employs the 1/2 coding rate, it is easy to determine the characteristics of the convolutional coding and to determine the number of redundant bits, and other coding rates can be converted by 1/2.

In one embodiment, the lowest constellation point is 4.

In one embodiment, the first signal includes ZigBee, bluetooth, 2.4GLoRa, or other signals with overlapping subcarriers with WiFi, and the method of the present invention may be adopted to reduce the WiFi signal power on the first signal channel by setting the constellation point with the lowest power, thereby reducing the interference of WiFi on the first signal link.

In a second aspect, the present invention provides a device, where the device is a WiFi router or a mobile phone, and the method is performed on the device to reduce the power of a WiFi signal.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive labor.

FIG. 1 is a schematic diagram of a standard WiFi transmission process;

FIG. 2 is a schematic diagram of overlapping of a WiFi channel and four ZigBee channels;

FIG. 3, CSMA/CA mechanism schematic;

FIG. 4, schematic diagram of WiFi transmission and additional bits added;

fig. 5, a schematic diagram of a spectrum with WiFi added extra bits;

fig. 6, schematic diagram of WiFi transmission and extra bit addition flow;

FIG. 7 is a schematic diagram of a WiFi spectrum after inserting valid bits;

fig. 8, 1/2 illustrate the convolutional encoding process.

Detailed Description

The technical solutions in the embodiments of the present application will be described clearly and completely with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only some embodiments of the present application, and not all embodiments.

The terms "first", "second" and "third" are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. The definitions of "first", "second" and "third" features may explicitly or implicitly include one or more of such features.

Fig. 1 is a standard WiFi transmission process. The data bits are first subjected to anti-interference by a channel coding module, and then converted into complex symbols after being modulated by QAM (Quadrature Amplitude Modulation). Then, QAM points are mapped to OFDM (Orthogonal Frequency Division Multiplexing) subcarriers through an S/P (serial to parallel) module, and output as time domain OFDM (Orthogonal Frequency Division Multiplexing) symbols after IFFT (Inverse Fast Fourier Transform) and P/S (parallel to serial) processing. Each OFDM (orthogonal frequency division multiplexing) symbol is inserted with a cyclic prefix to eliminate inter-symbol interference. The signal is finally transmitted through the radio frequency front end. It is noted that OFDM enables a device to transmit multiple orthogonal sub-carrier signals, closely spaced, to transmit data in parallel.

The first signal in the present invention includes ZigBee, bluetooth, 2.4GLoRa, or the like.

In the following, the WiFi signal power on the ZigBee channel is taken as an example.

WiFi working in 2.4GHz ISM frequency band has different specifications for ZigBee signals. On the physical layer, WiFi employs OFDM (orthogonal frequency division multiplexing) and QAM (quadrature amplitude modulation) modulation, while ZigBee employs DSSS (Direct Se-sequence Spread Spectrum) and OQPSK (offset quadrature phase shift keying) modulation. In addition to that, they have different channel bandwidths. ZigBee has 16 2MHz channels, the channel interval is 5MHz, and the number is 11 ~ 26. WiFi has 13 20MHz channels and a 25MHz channel spacing, each channel being divided into 64 subcarriers, including 48 subcarriers, 4 subcarriers, and 12 subcarriers. Thus, one WiFi channel overlaps with four ZigBee channels. Each WiFi channel containing 64 sub-carriers overlaps with 4 ZigBee channels in the same way as shown in fig. 2.

For convenience of description, the four ZigBee channels are abbreviated as CH1, CH2, CH3, and CH 4. It can be seen from fig. 2 that CH1-CH3 overlap with one pilot subcarrier, and CH4 overlap with a zero subcarrier. Moreover, the transmission power of both devices is asymmetric. The transmission power of the ZigBee equipment is not more than 0dBm so as to reduce energy consumption; and the WiFi transmission power can reach 20dBm, so that the purpose of large coverage is achieved.

On the MAC layer, both WiFi and ZigBee networks use CSMA/CA (Carrier Sense Multiple Access with Collision avoidance) mechanisms to contend for the channel. The detailed CSMA/CA mechanism is shown in fig. 3. When a device starts to transmit a packet, it first waits for a DIFS (Distributed Inter-frame Spacing) time; if the channel is idle during DIFS, the device then waits a random duration, which includes a number of back-off times, for the channel; when the channel of the rollback slot is idle, the rollback timer is decreased by 1, and when the channel is busy, the rollback timer is frozen; when the back-off timer is zero, the device may eventually send a packet. During the DIFS or each backoff slot, the device should perform CCA (Clear Channel Assessment) to determine whether the Channel is idle. Determining that the channel is idle if the detected signal energy is below a predefined threshold; otherwise it is busy.

The main differences between WiFi and ZigBee here are: WiFi DIFS is 28 μ s, ZigBee DIFS is 320 μ s, WiFi backoff time slot is 9 μ s or 20 μ s, and ZigBee backoff time slot is 320 μ s. This results in extremely unfair channel competition, and the WiFi devices are always able to get a channel for transmission.

By adopting the method of the invention, the WiFi signal power on the ZigBee channel is reduced, and the constellation point with the lowest power is arranged in the overlapped subcarrier of the WiFi and the ZigBee to reduce the WiFi signal power on the ZigBee channel, so that the interference of the WiFi to the ZigBee link is reduced, the successful transmission of the ZigBee is facilitated, the performance of the ZigBee network is improved, more transmission opportunities are provided, and the cross-protocol interference is avoided.

The method is compatible with WiFi and ZigBee standards of a physical layer and a MAC layer, and can be easily deployed to commercial equipment without additional hardware. Namely: the power of WiFi signals on a ZigBee channel is reduced by arranging the constellation point with the lowest power in the overlapped subcarriers of WiFi and ZigBee, so that the interference of the WiFi to a ZigBee link is reduced, and the successful transmission of the ZigBee is facilitated.

Specifically, when the method of the present invention is used to reduce the WiFi signal power on the ZigBee channel, the convolutional coding is used with 1/2 coding rate as an example, and details the process of determining to insert extra bits. Other code rates may be transformed by 1/2 to achieve a simplified calculation of the reverse-biased effective bits.

First, the lowest constellation point of a specific subcarrier required in the last OFDM modulation is determined as shown in fig. 4, and QAM points of overlapping subcarriers are four points with the lowest power. Taking QAM-16 as an example, each point carries four bits, but only two bits are important, which can minimize power, and therefore these two bits are taken as the valid bit set, as shown by the shaded bits in fig. 5. Similarly, there are 4 and 6 valid bits per QAM-64 and QAM-256 points, respectively. All that is done is to insert extra bits so that the valid bits are the designated bits, while the other bits in the QAM (quadrature amplitude modulation) points can be arbitrary.

And determining the constellation point with the lowest power after determining the required lowest constellation point of the specific subcarrier and the overlapping channel condition of the WiFi and the first signal. By determining the constellation point with the lowest power, the effective bit set in each constellation point before QAM modulation is determined. Since the interleaver maps the input bits to the output bits one by one according to a certain rule, an effective bit set before interleaving can be obtained. The value and position of the k-th significant bit before the interleaver are respectively denoted as v _k ，p _k Where K is [1, K ]]And K is the total number of valid bits to be inserted.

Although the convolutional encoder increases the redundancy of data bits and cannot generate any bit sequence, since the interleaving process is used to reduce decoding errors, the effective bits that are previously gathered together can be dispersed to different positions far away, so that the convolutional encoder can also determine additional bits.

According to the valid bit v _k ，p _k The procedure for determining the extra bits that need to be inserted in the WiFi bit data is as follows:

(1) the 1/2 rate convolutional encoding process is shown in fig. 8.

In the 1/2 rate convolutional encoding process, two generator polynomials g0 ═ (1011011) are used ₂ And g1 ═ (1111001) ₂ . The convolutional coding equation is shown below as Eq.1, one input bit x _n Triggering two coded bits y _2n-1 And y _2n ：

Wherein GF (2) is a Galois field. X _n The bit data before being input into the convolutional coding module is also the data after the WiFi bit data scrambling.

(2) Establishing the position relationship between the input bit and the effective bit, the method of the present invention is implemented

(symbol)

Indicating rounding up. Table 1 lists an example of the significant bits in the first OFDM symbol, where QAM-16 is used, and the ZigBee channel is CH2, where there are 14 significant bits.

TABLE 1

As can be seen from table 1, the effective ratio has two cases. The first case is that given an n, y is given in equation 1 _2n Or y _2n-1 One of which is a valid bit and the other is arbitrary. For example, when k is 9, n is 63, and p _k This case is considered as a single valid bit, 2n-1 125. The second case is then y _2n And y _2n-1 Are all valid bits, e.g. when k is 1 and k is 2, n is 15, which is considered as a double valid bit.

(3) In the current implementation, convolutional coding encodes and outputs 7 input bits, so that the output bits are not only matched with the current input bit x _n Determined and made up of a small number of past bits x _n-1 ～x _n-6 And (6) determining. Current bit x _n Is the input convolutionally encoded bits of fig. 6, and can also be considered as the output bits of the WiFi data after payload encoding and scrambling.

Using data obtained after scrambling WiFi bit data as a first bit set, using an effective bit set in front of an interleaver as a second bit set, and recording elements in the second bit set as { v } _k ，p _k }(k∈[1，K])，v _k And p _k Respectively representing the value and position of the K-th effective bit before the interleaver, and K being the total number of effective bits.

And setting a third bit set as a data set for carrying out payload coding on the WiFi bit data and then scrambling. One way of implementing the setting of the third bit set is that the third bit set is initially an empty set, and one bit of data is added after each judgment. In another implementation mode, the size of the third bit set is set according to the sizes of the first bit set and the second bit set, initial values are given to set elements, and the values are updated after each judgment. There are other implementations, which are not described in detail herein. In the following, taking the second implementation as an example, the initial value of the third bit set element is arbitrary.

(3.1) obtaining a first bit data x 'of a first set of bits' ₁ For the current first bit, the first bit of the third set of bits is taken as x ₁ Taking the third bit as the current third bit, and obtaining the position of the first effective bit as the current second bit position p ₁ 。

From the current third bit x _n And the current second bit position p _k The corresponding relation of (2) to determine whether additional bits need to be inserted.

(3.2) if the index n of the current third bit is not equal to the second bit position p _k Then no extra bit needs to be inserted, now having the current third bit x _n Is equal to a first bit x' _i The value range of i is 1, 2, …, N' is the total number of WiFi bit data, and the value range of N is 1, 2, …, N is the size of the third bit set finally obtained.

Then obtaining the next first bit x' _i+1 Let it be the current first bit. And (3) repeatedly executing (3.2) the step of acquiring a position of one bit in the third bit set as the current third bit.

(3.3) passing the current third bit x _n And the current second bit position p _k The corresponding relation of (a) is judged as inserting a single significant bit, specifically:

if 2n-1 etcAt the second bit position p _k Then the following formula is calculated to obtain the insertion bit etr 0:

if 2n is equal to the second bit position p _k Then the following formula is calculated to obtain the insertion bit etr 0:

post-computation adjusting the position of elements in the set of transmit bits, causing additional bits to be inserted into the transmit bits, and causing the current first bit x' _i Is assigned to the current third bit x _n . And acquiring the next bit in the original bit set as a current first bit and acquiring the next second bit as a current second bit. Obtaining the next bit in the third bit set as the current third bit, and repeating the steps (3.2)

(3.4) starting from the current third bit x _n And the current second bit position p _k The above formula (eq.1) disperses the effective bits far enough due to the interleaving process, thereby avoiding the situation that there is no solution, and no matter what kind of QAM modulation (quadrature amplitude modulation) and ZigBee channel combination, the double effective bits can be satisfied by inserting two extra bits at the specified position. Therefore, in either case, one more valid bit can be satisfied by inserting one more bit on the WiFi bit data. The extra bits can also be designated as other positions when solving, which does not change the implementation principle of the method of the present invention for reducing the power of the WiFi signal on the first signal channel by setting the constellation point with the lowest power in the overlapping subcarriers of the WiFi and the first signal.

Specifically, a value v of a current second bit corresponding to the current second bit position is obtained _k And the value v of the next second bit position _k+1 They are the convolution encoded output bits. Make them pass throughSubstituting the formula to obtain extra bits etr0, etr 1;

inserting additional bits into the third set of bits after calculation, and current first bit x' _i Is assigned to the current third bit x _n . And acquiring the next bit in the first bit set as a current first bit, and acquiring the 2 nd effective bit after the current second bit as a current second bit. And acquiring the next bit data from the third bit set as the current third bit, and repeating the operation (3.2).

When all first bits are set { x' _i When the value of the bit is traversed, a third bit set { x } is finally obtained _n }，n∈[1，N]The third set of bits inserts a set of extra bits for the first set of bits, as shown in the schematic code of table 2 below. { x _n And { x' _i Are scrambled data, the transmit bits in fig. 6 are passed through the pair x _n And obtaining the descrambling code.

Because the scrambler is used for avoiding the occurrence of long strings of 0 or 1 bits, the scrambler maps the input bits to the output bits one by one according to a certain rule, so that the method can determine the output bits inserted with the effective bits, determine the value of the effective bits and the positions to be inserted, encode the WiFi effective load and generate the transmission bits.

The process of determining the effective bits by the method of the present invention is shown in fig. 6, when the transmission bits pass through the standard WiFi transmission process, the overlapped subcarriers are filled with the lowest constellation points, the implemented WiFi spectrogram is shown in fig. 7, and the spectrum power of the overlapped part is greatly reduced compared with the surrounding spectrum power.

TABLE 2

The method is verified by a radio platform based on USRP software and commercial ZigBee, is compatible with WiFi and ZigBee standards of a physical layer and a MAC layer, can be easily deployed to commercial equipment without additional hardware, and has smaller WiFi loss throughput than the prior art. The commercial devices include WiFi routers, cell phones, etc.

By encoding the WiFi load, the subcarrier level energy of the WiFi is reduced, and therefore the mechanism of slow protocol interference is effectively relieved.

Through the above description of the embodiments, those skilled in the art will clearly understand that the method of the present disclosure may be implemented by software plus necessary general hardware, and may also be implemented by special hardware including special integrated circuits, special CPUs, special memories, special components and the like. Generally, functions performed by computer programs can be easily implemented by corresponding hardware, and specific hardware structures for implementing the same functions may be various, such as analog circuits, digital circuits, or dedicated circuits. However, software program implementation is a more preferred implementation for more of the present disclosure.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the above-described embodiments and application fields, and the above-described embodiments are illustrative, instructive, and not restrictive. Those skilled in the art, having the benefit of this disclosure, may effect numerous modifications thereto without departing from the scope of the invention as defined by the appended claims.

Claims

1. A method for realizing cross-protocol coexistence based on WiFi payload coding is characterized in that for a first signal interfered by a WiFi signal, a constellation point with the lowest power is set in a subcarrier where the WiFi and the first signal are overlapped, and the power of the WiFi signal on a first signal channel is reduced.

2. The method of claim 1, wherein the setting comprises the steps of:

the set of valid bits is made the specified set of bits.

3. The method of claim 2, wherein the specified set of bits is obtained by:

4. The method of claim 3, wherein the extra bits are obtained by:

acquiring first data in a third bit set as a current third bit;

if the number of the extra bits to be inserted is M1, M1 is greater than 0, and M2-M1 third bits used for the convolutional code conversion are obtained from the third bit set according to the number of the M2 bits used for the convolutional code conversion, wherein M2 is greater than 0; acquiring the next second bit from the current second bit in the second bit set until M1-1 second bits are acquired, and substituting the values of the M2-M1 third bits and the M1 second bits into a convolutional coding equation or a convolutional coding equation set to solve extra bits;

5. The method of claim 1, wherein the constellation points are 4.

6. The method of claim 1, wherein the first signal comprises ZigBee, bluetooth, or 2.4 GLoRa.

7. The method of claim 3 wherein said convolutional encoding uses an 1/2 code rate.

8. A device, the device being a WiFi router or handset, wherein the method of any of claims 1-7 is performed on the device to reduce the power of a WiFi signal.